Some older Mail messages moved to Junk folder after MacOS 26.6 update

[jdw13]

This may be unrelated to the update, but want to give people a 'heads up' as the timing is suspicious.
I updated a couple of M1 computers to MacOS 26.6 last night, and this morning I noticed some older email messages had moved from inbox to the Junk folder. At first I thought maybe there was new feature to move year-old email to junk automatically, but that would be a very bad thing to do with an update. {it was not all the older mail, but most of the 'moved' messages seemed to be part of a common thread, so something I did is not completely impossible}

It could be operator error (Me), but Mail has done strange things to me like show the header of one message with the body of another (column layout). I do use email in non-recommended ways like over 350 rules that mostly move messages to different folders.
The Mail Application has been very good and stable for me in MacOS 26, but in the past when it got confused, having Onyx delete the indices would fix things up.

Please let us know you notice anything strange like this after you update to 26.6.

 

[benholt]

Two culprits worth checking before you go rebuilding the envelope index. With 350 rules, look at Mail > Settings > Rules for anything with 'Move to Junk' as an action — after an update Mail re-evaluates rules against messages whose mailbox state got touched during account resync, so a 'to Junk' rule that was being short-circuited earlier by an ordered predecessor can suddenly catch a bunch. Second, check Mail > Settings > Junk Mail: if the Bayesian filter is on with 'Perform custom actions' selected, it re-scores messages when their envelope state changes, which happens en masse after a major update — and that would fit the 'part of a common thread' pattern since Bayes bundles by similarity score. If neither turns up the answer, quit Mail and delete the Envelope Index files (Envelope Index, -shm, -wal) in ~/Library/Mail/V*/MailData/ so the index rebuilds clean.